Surface free energy and microarray deposition technology

Microarray techniques use a combinatorial approach to assess complex biochemical interactions. The fundamental goal is simultaneous, large-scale experimentation analogous to the automation achieved in the semiconductor industry. However, microarray deposition inherently involves liquids contacting solid substrates. Liquid droplet shapes are determined by surface and interfacial tension forces, and flows during drying. This article looks at how surface free energy and wetting considerations may influence the accuracy and reliability of spotted microarray experiments

Die Beziehungen der Norddeutschen Wollkämmerei und Kammgarnspinnerei zu den Banken

The Relationship of the Norddeutsche Wollkämmerei und Kammgarnspinnerei (Nordwolle Group) with the Banks: Research into the relationship between banking and industry has long held the view that banks had dominated their clientele from industry, trade and retailing and they had established a position of power that was almost impossible to reign in. More recent studies question this assessment and deliver impressive evidence that the relationship between industry and banks was often characterized by information asymmetries. For example, major companies often withheld information about their earnings performance during credit negotiations so that the banks had to make large risk provisions which reduced their profitability. This was also true for the Nordwolle textile group, which had financed the expansion of its business during the Weimar Republic primarily from outside capital, first and foremost using loans from various banks. In obtaining these loans, the Group's management succeeded repeatedly in playing competing banks against one another. Even major banks such as Danat-Bank, Berliner Handelsgesellschaft, and probably Dresdner Bank as well, placed major bets on getting Nordwolle to commit itself as a client. As long as the banks could be talked into believing that company was profitable and continually expanding, the banks were ready to grant new loans. Not until the spring of 1931, after indications about the Group's actual situation had made the rounds did the banks push through extensive audits of the company's financial statements. That the efforts to rescue Nordwolle ultimately remained fruitless was not least a result of the new-found caution in awarding additional loans

Dynamics of Fluid Vesicles in Flow through Structured Microchannels

The dynamics of fluid vesicles is studied under flow in microchannels, in which the width varies periodically along the channel. Three types of flow instabilities of prolate vesicles are found. For small quasi-spherical vesicles -- compared to the average channel width -- perturbation theory predicts a transition from a state with orientational oscillations of a fixed prolate shape to a state with shape oscillations of symmetrical ellipsoidal or bullet-like shapes with increasing flow velocity. Experimentally, such orientational oscillations are observed during the slow migration of a vesicle towards the centerline of the channel. For larger vesicles, mesoscale hydrodynamics simulations and experiments show similar symmetric shape oscillation at reduced volumes $V^* \gtrsim 0.9$. However, for non-spherical vesicles with $V^* \lesssim 0.9$, shapes are found with two symmetric or a single asymmetric tail.Comment: 6 pages, 6 figure

Label-free microfluidic enrichment of ring-stage Plasmodium falciparum-infected red blood cells using non-inertial hydrodynamic lift

<b>Background</b> Understanding of malaria pathogenesis caused by Plasmodium falciparum has been greatly deepened since the introduction of in vitro culture system, but the lack of a method to enrich ring-stage parasites remains a technical challenge. Here, a novel way to enrich red blood cells containing parasites in the early ring stage is described and demonstrated.<p></p> <b>Methods</b> A simple, straight polydimethylsiloxane microchannel connected to two syringe pumps for sample injection and two height reservoirs for sample collection is used to enrich red blood cells containing parasites in the early ring stage (8-10 h p.i.). The separation is based on the non-inertial hydrodynamic lift effect, a repulsive cell-wall interaction that enables continuous and label-free separation with deformability as intrinsic marker.<p></p> <b>Results</b> The possibility to enrich red blood cells containing P. falciparum parasites at ring stage with a throughput of ~12,000 cells per hour and an average enrichment factor of 4.3 ± 0.5 is demonstrated.<p></p> <b>Conclusion</b> The method allows for the enrichment of red blood cells early after the invasion by P. falciparumparasites continuously and without any need to label the cells. The approach promises new possibilities to increase the sensitivity of downstream analyses like genomic- or diagnostic tests. The device can be produced as a cheap, disposable chip with mass production technologies and works without expensive peripheral equipment. This makes the approach interesting for the development of new devices for field use in resource poor settings and environments, e.g. with the aim to increase the sensitivity of microscope malaria diagnosis.<p></p&gt